After our careful description of the remains left by the city of Sargon we need enter into few details as to the other fortified _enceintes_ that have been explored in Mesopotamia. The same rectangular plan, the same thick walls and carefully arranged gateways are to be found in them all. With the Assyrians as with their neighbours, every town was fortified. The square form seems to have been universally employed for the flanking towers. It is quite by exception that we find in one of the pictures of a siege on the Balawat gates, tall and slender towers that appear to be round on plan and to be much higher than the curtain they defend (Fig. 28). Besides these town walls there were, no doubt, at the mouths of the valleys opening into the basin of the Tigris, strong forts and isolated towers, perched upon some abrupt rock or ridge: the siege of such a fortress seems to be going on in the relief figured on the next page (Fig. 29). The platform at the top of the tower seems to be raised and strengthened by a structure of wood, which stands out beyond the crenellations and is protected by a row of shields, like the bulwarks of a Roman galley. This contrivance resembles those _ourdeys_ of which the military engineers of the middle ages made such constant use. The garrison still show a bold front from behind their defences, but the women and old men, foreseeing the fall of their stronghold, are decamping while there is yet time. [Illustration: FIG. 28.--Fortified wall; from the Balawat gates. British Museum.] The military successes of the Assyrians are partly to be explained by their engineering skill. In all that concerned the attack and defence of places they seem to have left the Egyptians far behind. In addition to mines and battering rams they employed movable towers which they pushed forward against such walls as they wished to attack point blank, and thought either too high or too well lined with defenders to be open to escalade (Vol. I., Fig. 26). In the relief partly reproduced on page 75, the defenders have not ceased their resistance, but in the lower section, in what we may call the _predella_ of the picture, we see a long band of prisoners of both sexes being led off by soldiers. These we may suppose to be captives taken in the suburbs of the beleaguered city, or in battles already won.[98] [Illustration: FIG. 29.--Siege of a fort; from Layard.]